In recent years, a communication system using a system such as W-CDMA (Wideband Code Division Multiple Access) has been developed as a third generation mobile communication unit. This provides services, such as audio communication, packet communication and the like, from a mobile communication network, to wireless communication terminals, such as cell phones and the like.
Conventionally, this kind of communication system is formed of a mobile communication network NW, having a cell phone 1 and a wireless base station 2 which is wirelessly connected to the cell phone 1, as shown in FIG. 8.
The mobile communication network NW is formed of the above-described wireless base station 2, a non-illustrative mobile communication control station, visited network mobile communication switching station, gateway mobile communication switching station, and general telephone line, etc.
In this communication system, a user who uses the cell phone 1 transmits an individual channel establishment request message from the cell phone 1 to the mobile communication network NW, when he/she wants to get the service, such as audio communication, packet communication, or the like (Phase A).
The mobile communication network NW informs the cell phone 1 of a plurality of set parameters (individual channel establishment parameters) for establishing an individual channel, correspondingly to an individual channel establishment request message A transmitted from the cell phone 1 (Phase B).
In the cell phone 1, connection is established in the individual channel so as to begin transmission of a predetermined message, using the informed individual channel establishment parameter (Phase C). As a result, the user of the cell phone 1 is provided with the services, such as the audio communication, packet communication, and the like.
FIG. 9 is a diagram showing an audio transmission sequence of a layer (hierarchy) level 3 based on 3GPP communication specification, TS25.331, for communication between the cell phone 1 and the mobile communication network NW shown in FIG. 8.
As shown in FIG. 9, once an individual channel establishment request message (rrc Connection Request) for requesting an audio communication service is issued from the cell phone 1, the first individual channel is established between the cell phone 1 and the mobile communication network NW, control data, such as individual identification (measurement Control) and authentication (security Mode Command, security Mode Complete) of the cell phone 1 and the like are transmitted between the cell phone 1 and the mobile communication network NW.
Now, for transmission of actual audio data between the cell phone 1 and the mobile communication network NW, the second individual channel is established. This second individual channel is maintained while providing the audio communication service, so as to establish the audio communication service.
In the establishment of the first individual channel, the cell phone 1 is informed of a plurality of set parameters for establishing the first individual channel from the mobile communication network NW, using an rrc (radio resource control, wireless resource control) Connection Setup message [1].
In response to this, when replying an rrc Connection Setup complete message [2] from the cell phone 1, transmission with the first individual channel begins, and the first individual channel is established.
In the establishment of the second individual channel, the cell phone 1 is informed of a plurality of set parameters for establishing the second individual channel using a radio Bearer Setup message [3] from the mobile communication network NW.
These set parameters correspond to a transmission reception individual channel for audio or packet data. In the cell phone 1, transmission with the second individual channel begins, and the second individual channel is established, using the informed plurality of set parameters.
In this case, the cell phone 1 is informed of transmission timing from the mobile communication network NW with the second individual channel, using the already-established first individual channel.
FIG. 10 is a sequence diagram for explaining operations of the cell phone 1 in the layer level 1 in the term from the reception of the Setup message [1] to transmission of the rrc Connection Setup complete message [2] in FIG. 9.
As shown in FIG. 10, the cell phone 1 sets the set parameters for establishing the first individual channel and included in the received rrc Connection Setup message [1] from the mobile communication network NW, into the layer (Layer) 1.
In the 3GPP communication specification, the timing for data transmission from the cell phone 1 with the first individual channel is based on the parameters, [PC (Packet Combining) preamble (0 to 70 msec) and SRB (Source Routing Bridging) delay (0 to 70 msec)], in the rrc Connection Setup message, thus is obtained with these two parameters [PC Preamble+SRB delay].
In the term of the parameter [PC Preamble], only the pilot bits of the individual control channel are transmitted. In the term of the parameter [SRB delay], no data transmission is performed with the first individual channel.
The time that is obtained based on the parameters [PC Preamble+SRB delay] is the time that is required when receiving data transmitted from the cell phone 1 with the first individual channel on the side of the mobile communication network NW.
Other than the above-described wireless communication terminal, conventionally, this kind of techniques is disclosed in the following documents.
In a spread spectrum communication system disclosed in Patent document 1, the sub station performs frame synchronization based on a downstream reference signal transmitted from the main station, and transmits an upstream control signal based on this frame synchronization. The main station obtains a propagation delay time in a wireless section from the relationship between a downstream control signal and the upstream control signal. The sub station transmits an upstream data signal in synchronization with a frame synchronization signal, and the main station receives the upstream data signal at timing in accordance with the propagation delay time.
The sub station performs frame synchronization based on the upstream reference signal transmitted from the main station, and transmits an upstream control signal based on this frame synchronization. The main station obtains the propagation delay time in a wireless section from the relationship between the downstream control signal and the upstream control signal, and gives information about the propagation delay time to the sub station through a downstream channel. The sub station transmits an upstream data signal at timing in accordance with the propagation delay time. Then, the main station receives the upstream data signal.
As a result, even in the case where a transmission path has a large delay, high speed synchronization of a long-cycle spread code is enabled without a large increase in the hardware scale.
According to a communication control method disclosed in Patent document 2, in the packet reception, a mobile station controls transmission power of an upstream individual channel based only on transmission power control information included in a downstream individual channel from a packet transmission base station.
Patent document 1: Japanese Unexamined patent publication NO. 2000-115029 (claims 1 and 5)
Patent document 2: Japanese Unexamined patent publication NO. 2004-007030 (claim 1).